Physics 2

A glass rod is rubbed with silk, and a plastic rod is rubbed with wool. Afterward, to which object or objects will the glass rod be attracted?

The silk and the plastic rod.

Two metal spheres (A and B) are connected by a conducting wire. A positively charged rod is brought close to sphere A but is not touching sphere A. Sphere B is farther away. With the rod still close, the wire between spheres is disconnected, and the rod is then removed. The rod never touched either sphere. What is true about the charge on the two spheres?

Sphere A carries some net negative charge; sphere B carries some net positive charge.

A certain electroscope is charged until it holds 0.10 mC of negative charge. Have electrons been added to the electroscope, or removed from it, and how many?

6.3×1014 electrons have been added.

What is the distance between a 10 μC charge and a 24 μC charge if the magnitude of the force between them is 1.2 mN?

0.23m

0.46m

1.2m

2.6m

23m

42m

F

There is a −4.00 nC charge at the origin. A 9.00 nC charge is on the x-axis at x=2.00m. A 5.00 nC charge is on the y-axis at y=−1.00m. What is the total force on the −4.00 nC charge at the origin? Give your answer as a magnitude and an angle counterclockwise from the positive x-axis.

1.97×10−7 N, 294°

What is the relationship between the gravitational force between two electrons, FG. and the electric force between two electrons, FE ?

FG/FE=2.4×10−43

A 1.2g plastic bead is given a charge of −14 nC by rubbing. What magnitude and direction of electric field is necessary to levitate the bead?

8.4×105 N/C, downward

A 3.0 nC charge is at the origin, a −12 nC charge is at x=2.0cm. Where, on the x-axis, could you place a −45 nC charge so that it would experience no net force?

x=−2.0cm

A water molecule is a dipole. If water were placed in the uniform field between capacitor plates, which of the following would best describe the force and torque experienced by the water molecules?

The force would be zero, and the torque would align the dipole moment with the electric field.

Each plate in a parallel-plate capacitor has an area of 12.5cm2. and the separation between plates is 0.822mm. The magnitude of the charge on each plate is 7.43 mC. What is the magnitude of the electric field between the plates and inside the metal of the plates?

Ebetween=6.72×1011 N/C; Ein plate=0 N/C